Gentlemen, isn't emacs rather rude when it second guesses the user's
idea of a good command to run:
$ mkdir x; cd x; touch a.tar
$ emacs -l dired-x .
! w c RET ! ESC p
It now already knows I want to use wc. However it insists mother
knows best and still offers tar.

Yes, M-p should put "wc" in the minibuffer. "tar xvf" should be available via
M-n.

I could have already used wc 1000
times and it still wouldn't get a hint about what I like.
Worse yet is when there are several of its "better choices", not just
one. In this case we have to plod thru each one of those with ESC p
till we get to the one we just used, now way in the back of the bus.
E.g. for .dvi, see dired-guess-shell-alist-default.
Note, if I used wc on tar files, and sum on cpio files, then if I am
on a cpio file, it should prompt like: sum, cpio -iv <, wc
In that order, I suppose.